We are studying how neurons interact with their target cells during synaptogenesis and the role of supporting cells such as Schwann cells in this process. We are particularly interested in how emerging patterns of neural activity affect the establishment and maintenance of synaptic connections. We use the connections between motor neurons and muscle fibers as a model system, due to their accessibility, relative simplicity of organization, and the ease with which the pre- and post-synaptic population can be manipulated. Confocal microscopy has been used in several aspects of this work and that of our collaborators: Studies of synaptogenesis during development and following reinnervation (N. Waran, undergraduate, and W. Thompson, Ph.D., Univ. of Texas at Austin) use confocal microscopy to determine the spatial relationship of synaptic components in fixed and living tissue. This work has been published in abstract form, in a review, and a paper is presently in preparation. Our studies of motor neuron development and gap junctional communication in spinal cord slices employ confocal microscopy to determine the morphology of motor neurons retrogradely labeled with calcium sensitive dyes (G. Bump, graduate student) or with other tracers (J. Pines, undergraduate). This work has been published in abstract form and a paper is presently in preparation. With Rebecca Hartely (graduate student) we are using immunohistochemistry and confocal microscopy to study the ability of transplanted precursor cells to make synapses with host spinal cord tissue. With Linda Bone (M.D./Ph.D. student) we are using confocal microscopy to study intracellular pathways for diffusion in myelinating Schwann cells in in vitro preparations of teased sciatic nerve axons. 8-31-96